Polymorphism of calcium carbonate was investigated using a constant-composition method, and three polymorphs—calcite, aragonite, and vaterite—are produced. Factors that affect the formation of polymorphs are studied over a wide range, including solution pH, temperature, concentration ratio of components, supersaturation, ionic strength, and type and concentration of additives. At room temperature, solution pH is the most significant factor, and high yield polymorphs are present at different pH values. At a high temperature, aragonite becomes the major product at a pH below 12. The effects of the additive are complicated, depending on its type and concentration as well as the operating conditions. The influence of concentration ratio and supersaturation on the formation of polymorphs is less significant, Besides, various particle morphologies of CaCO3 polymorphs are observed, depending on the operating conditions.